The invention relates to a display device for systems, in particular of a motor vehicle, which generates a warning signal or fault signal when there are predefined operating states and/or deviations from a set point operating state. These systems have a control device which is connected upstream of the display device and which stores the previously mentioned warning signals or fault signals.
Display devices and fault displays are generally customary in motor vehicles such as, for example, brake lining wear displays. In such displays a signalling light or the like is immediately switched on whenever the thickness of one of the brake linings (or pads) of a vehicle service brake drops below a predefined value.
Furthermore, motor vehicles may be equipped with monitoring devices which interrogate the respective operating state or fault signals of the motor vehicle systems which are generally specified, and store corresponding data over the long term. These data can then be displayed and/or converted into fault signals with a separate interrogation unit. Moreover, when a fault occurs, a display can be activated immediately. Appropriate arrangements are the subject-matter of German Patent document DE 32 29 411 A1 (having a counterpart in U.S. Pat. No. 5,019,799).
German Patent document DE 31 21 645 C2 discloses computer-aided control systems which are used for, among other things, controlling the engine and/or for controlling the ignition of the engine. They are also used for monitoring various vehicle systems and, in the process, storing status data and fault signals. In this way, the working capacity of the control systems can also be used for diagnostic purposes, i.e. the diagnostic interrogations can be carried out in the intervals between the control measures.
German Patent document DE 39 02 339 A1 relates to the acquisition of data in a battery-driven electric vehicle. Here, all the data of the vehicle and of the battery are collected and processed in an information processor and information store, and transmitted from there to a data evaluation unit.
The German Publication by B. Eberwein, W. Dorks entitled "Onboard--Diagnose--Ein Weg zu hoherer Fahrzeugverfugbarkeit (On board diagnostics--a way of improving vehicle availability)" in "nachverkehrs-praxis (local) traffic practice)" No. 9/1995, pages 268 to 270, relates generally to the usefulness of automatic diagnostic systems in vehicles. They enable the maintenance of a fleet of vehicles to be significantly simplified.
European Patent document EP 0 308 944 A2 describes a fault diagnostic device for a vehicle control system. Here, fault messages are stored and recalled before repair or maintenance work is performed. In this context, EP 0 308 944 A2 treats the problem of preventing fault information which is erroneously stored from being displayed. For this purpose, it is proposed to suppress the display of an item of fault information if the fault message is not repeated within a predefined time period. However, suppressed fault information can also be displayed again, in order, for example, to facilitate the diagnostic work of a workshop. As soon as the vehicle's engine is switched off (via the ignition switch), the vehicle control system and the fault diagnostic device are shut down.
U.S. Pat. No. 4,447,801 relates to a diagnostic system which, when the ignition of a vehicle engine is switched on, illuminates appropriate displays if a fault is detected. In this context, mention is made of the problem wherein a driver typically tends to ignore such warning displays because too many displays are illuminated at the same time. U.S. Pat. No. 4,447,801 proposes various approaches to overcoming this problem:
(1) The warning displays may be generally tested before the vehicle is activated. PA1 (2) Furthermore, the warning displays can be tested successively before the vehicle is activated. PA1 (3) In addition, the warning displays can be switched on simultaneously and then successively switched off when the vehicle is activated. PA1 (4) Finally, the warning displays can be activated successively at the request of the driver.
In each case, the warning displays may relate to status variables which are independent of the running of the vehicle engine.
There is therefore needed a display device which can advantageously avoid unnecessary distractions of the person monitoring the display device or of the driver of a motor vehicle.
These needs are met according to the invention by providing a display device having a control device, connected upstream of the display device, which stores warning signals and fault signals, and at least temporarily activates the display device when a switching-off signal which is generated when there is an operational shut-down of the monitored system or motor vehicle is received.
The invention is based on the general idea that operational states, which make measures necessary or desirable only after a relatively long delay, are displayed only when operation is terminated so that, in the example of a motor vehicle, only signals which are actually important are displayed to the driver while driving. This takes into account that it is as a rule desirable to monitor diverse systems and functions in a vehicle, but that the associated signal displays may distract the driver if they occur "at the wrong time". At the same time, allowance is made for the fact that a signal display which occurs continuously may easily be disregarded by the driver.
In the invention, it is advantageous that the activation of the display device during an operational shut-down particularly ensures that attention is paid to the display.
The invention provides the advantage that, if necessary, very diverse functions can be monitored, and signals can then also be generated if there is no direct need for action. This is because, owing to the invention, the signals cannot cause the operator or driver to be distracted during operation.
This also allows for the fact that a large number of systems are of redundant configurations so that relatively minor malfunctions of subsystems are in themselves negligible, but it should equally well be possible to detect them so that in each case preventive measures can be taken within an appropriate time frame.
According to one advantageous embodiment of the invention there may also, if appropriate, be provision for the display device or fault display to be activated briefly when a corresponding signal occurs, even when the respective system is operating, and to be activated again in the event of an operational shut-down.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.